1 /*
2 * Copyright (C) 2004 Joakim Tjernlund
3 * Copyright (C) 2000-2005 Erik Andersen <andersen@uclibc.org>
4 *
5 * Licensed under the LGPL v2.1, see the file COPYING.LIB in this tarball.
6 */
7
8 /* These are carefully optimized mem*() functions for PPC written in C.
9 * Don't muck around with these function without checking the generated
10 * assembler code.
11 * It is possible to optimize these significantly more by using specific
12 * data cache instructions(mainly dcbz). However that requires knownledge
13 * about the CPU's cache line size.
14 *
15 * BUG ALERT!
16 * The cache instructions on MPC8xx CPU's are buggy(they don't update
17 * the DAR register when causing a DTLB Miss/Error) and cannot be
18 * used on 8xx CPU's without a kernel patch to work around this
19 * problem.
20 */
21
22 #include <string.h>
23
24 /* PPC can do pre increment and load/store, but not post increment and
25 load/store. Therefore use *++ptr instead of *ptr++. */
memcpy(void * to,const void * from,size_t len)26 void *memcpy(void *to, const void *from, size_t len)
27 {
28 unsigned long rem, chunks, tmp1, tmp2;
29 unsigned char *tmp_to;
30 unsigned char *tmp_from = (unsigned char *)from;
31
32 chunks = len / 8;
33 tmp_from -= 4;
34 tmp_to = to - 4;
35 if (!chunks)
36 goto lessthan8;
37 rem = (unsigned long )tmp_to % 4;
38 if (rem)
39 goto align;
40 copy_chunks:
41 do {
42 /* make gcc to load all data, then store it */
43 tmp1 = *(unsigned long *)(tmp_from+4);
44 tmp_from += 8;
45 tmp2 = *(unsigned long *)tmp_from;
46 *(unsigned long *)(tmp_to+4) = tmp1;
47 tmp_to += 8;
48 *(unsigned long *)tmp_to = tmp2;
49 } while (--chunks);
50 lessthan8:
51 len = len % 8;
52 if (len >= 4) {
53 tmp_from += 4;
54 tmp_to += 4;
55 *(unsigned long *)(tmp_to) = *(unsigned long *)(tmp_from);
56 len -= 4;
57 }
58 if (!len)
59 return to;
60 tmp_from += 3;
61 tmp_to += 3;
62 do {
63 *++tmp_to = *++tmp_from;
64 } while (--len);
65
66 return to;
67 align:
68 /* ???: Do we really need to generate the carry flag here? If not, then:
69 rem -= 4; */
70 rem = 4 - rem;
71 len -= rem;
72 do {
73 *(tmp_to+4) = *(tmp_from+4);
74 ++tmp_from;
75 ++tmp_to;
76 } while (--rem);
77 chunks = len / 8;
78 if (chunks)
79 goto copy_chunks;
80 goto lessthan8;
81 }
82 libc_hidden_def(memcpy)
83